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[h=2]DTC P1446 or P1447[/h] [h=3]Diagnostic Instructions[/h]
Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
Review Strategy Based Diagnosis for an overview of the diagnostic approach.
Diagnostic Procedure Instructions provides an overview of each diagnostic category.
[h=3]DTC Descriptors[/h]DTC P1446 00: Pre-Catalyst Temperature Too Low During Regeneration Malfunction

DTC P1447 00: Pre-Catalyst Temperature Too High During Regeneration Malfunction

[h=3]Circuit/System Description[/h]The diesel exhaust after-treatment system consists of an under hood pre-catalytic converter and an underbody catalytic converter. The underbody catalytic converter also consists of the main diesel oxidation catalyst and the coated Diesel Particulate Filter (DPF). One of the main purposes of the DPF is to collect particulates from the engine exhaust in order to minimize discharge of soot to the atmosphere. The soot particles accumulate in the channels of the DPF and are burned off at regular intervals through a process called regeneration. This prevents the DPF from clogging. The ECM commands the DPF regeneration after calculating various vehicle conditions such as DPF pressure difference, exhaust gas temperature, engine oil quality, engine speed, etc. Excessive accumulation of the soot in the DPF can cause a drop in the engine performance. During regeneration, additional fuel is injected via multiple post injections in order to increase the exhaust gas temperature. During this period, the DPF temperature is raised to approximately 600°C (1112°F) and the accumulated soot is oxidized or burned off into carbon dioxide (CO2).
[h=3]Conditions for Running the DTC[/h]The DTC runs during the DPF regeneration process.
[h=3]Conditions for Setting the DTC[/h][h=4]P1446[/h]The actual temperature of the exhaust gas temperature sensor 1 is 200°C (392°F) less than the desired temperature.
[h=4]P1447[/h]The actual temperature of the exhaust gas temperature sensor 1 is 100°C (212°F) greater than the desired temperature.
[h=3]Action Taken When the DTC Sets[/h]DTCs P1446 and P1447 are Type A DTCs.
[h=3]Conditions for Clearing the DTC[/h]DTCs P1446 and P1447 are Type A DTCs.
[h=3]Diagnostic Aids[/h]
If the engine has sat overnight, both exhaust gas temperature sensors and the Engine Coolant Temperature (ECT) sensor values should display within 3°C (5°F).
After starting a cold engine, the exhaust gas temperature sensors temperature should rise steadily, then stabilize.
High resistance in the circuits of either of the exhaust gas temperature sensors could set a DTC.
[h=3]Reference Information[/h][h=4]Schematic Reference[/h] Engine Controls Schematics
[h=4]Connector End View Reference[/h] Component Connector End Views
[h=4]Electrical Information Reference[/h]
Circuit Testing
Connector Repairs
Testing for Intermittent Conditions and Poor Connections
Wiring Repairs
[h=4]DTC Type Reference[/h] Powertrain Diagnostic Trouble Code (DTC) Type Definitions
[h=4]Scan Tool Reference[/h] Control Module References for scan tool information
[h=3]Circuit/System Verification[/h]
  1. Ignition On, observe the DTC information with a scan tool. Verify no other DTCs are set.
    If any other DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle for further diagnosis.
  2. Engine running, perform a regeneration procedure with a scan tool. Observe the DTC information with a scan tool. DTCs P1446 or P1447 should not set.
  3. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
[h=3]Circuit/System Testing[/h]
  1. Ignition OFF, disconnect the harness connector at the appropriate B131 Exhaust Temperature Sensor.
  2. Test for less than 5 Ω between the low reference circuit terminal 1 and ground.
    If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the K20 Engine Control Module.
  3. Ignition ON, verify the scan tool exhaust gas temperature sensor parameter is at 5 V.
    If less than the specified range, test the signal circuit for a short to ground. If the circuit tests normal, replace the K20 Engine Control Module.
    Note: If the fuse in the jumper wire opens, the signal circuit is shorted to a voltage and the sensor may be damaged.
  4. Install a 1 A fused jumper wire between the signal circuit terminal 2 and ground. Verify the scan tool exhaust gas temperature sensor parameter is at 0 V.
    If greater than the specified range, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K20 Engine Control Module.
  5. Inspect for the following conditions:
    Intake and exhaust system for leaks or restrictions

    Fuel system for leaks or restrictions

    Excessive water in fuel

    Exhaust Gas Recirculation (EGR) for normal operation

    Plugged fuel filter

    Restricted air filter

    Turbocharger operation

    An engine mechanical condition

    If a condition is found, repair as necessary.
  6. If all circuits test normal, test or replace the B131 Exhaust Temperature Sensor.
[h=3]Repair Instructions[/h]Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Exhaust Temperature Sensor Replacement - Position 1 .
Exhaust Temperature Sensor Replacement - Position 2 .
Control Module References for ECM replacement, programming and setup
[h=3]Repair Verification[/h]Ignition ON, observe the scan tool DPF accumulated soot mass parameter. The parameter should be less than 10 g.
If greater than the specified range, perform a DPF service regeneration. Refer to Exhaust Particulate Filter Cleaning .
 
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